Cabazitaxel is chemically, (2α,5β,7β,10β,13α)-4-acetoxy-13-({(2R,3S)-3[(tertbutoxycarbonyl)amino]-2-hydroxy-3-phenylpropanoyl}oxy)-1-hydroxy-7,10-dimethoxy-9-oxo-5,20-epoxytax-11-en-2-yl benzoate and has the structural formula:

Cabazitaxel is a drug for the treatment of hormone-refractory prostate cancer. It is marketed by Sanofi Aventis under the brand name JEVTANA®.
Cabazitaxel and its process were disclosed in U.S. Pat. No. 5,847,170 ('170 patent). According to '170 patent also described a process for the preparation of 4α-acetoxy-2α-benzoyloxy-5β,20-epoxy-1β,13α-dihydroxy-7β,10β-dimethoxy-9-oxo-11-taxene.
According to the '170 patent, cabazitaxel can be prepared by reacting 4α-acetoxy-2α-benzoyloxy-5β,20-epoxy-1β-hydroxy-7β,10β-dimethoxy-9-oxo-11-taxen-13α-yl(2R,4S,5R)-3-tert-butoxycarbonyl-2-(4-methoxyphenyl)-4-phenyl-1,3-oxazolidine-5-carboxylate with hydrochloric acid in ethanol.
U.S. Pat. No. 5,962,705 described a process for the preparation of 4α-acetoxy-2α-benzoyloxy-5β,20-epoxy-1β,13α-dihydroxy-7β,10β-dimethoxy-9-oxo-11-taxene can be prepared by reacting 4α-acetoxy-2α-benzoyloxy-5β,20-epoxy-1β,7β,10β,13α-tetrahydroxy-9-oxo-11-taxene with methyl iodide in the presence of sodium hydride and tetrahydrofuran, maintained for 7 hours 30 minutes and then poured into water and diisopropyl ether, and isolating.
U.S. patent application publication no. 2012/0149925 described a processes for the preparation of 4α-acetoxy-2α-benzoyloxy-5β,20-epoxy-1β,13α-dihydroxy-7β,10β-dimethoxy-9-oxo-11-taxene. According to the patent application also disclosed a process for the preparation of cabazitaxel can be prepared by reacting 1-hydroxy-7β,10β-di-methoxy-9-oxo-5β,20-epoxytax-11-ene-2α,4,13α-triyl-4-acetate-2-benzoate-13-{(2R,3S)-3-[(tert-butoxycarbonyl)amino]-2-triethylsilyloxy-3-phenylpropanoate} with hydrochloric acid in methanol and then quenched with sodium bicarbonate.
Processes for the preparation of 4α-acetoxy-2α-benzoyloxy-5β,20-epoxy-1β,13α-dihydroxy-7β,10β-dimethoxy-9-oxo-11-taxene were described in International patent application publication no. WO 2012/142117.
U.S. patent application publication no. 2013/090484 disclosed a process for the preparation of 4α-acetoxy-2α-benzoyloxy-5β,20-epoxy-1β,13α-dihydroxy-7β,10β-dimethoxy-9-oxo-11-taxen. According to the patent application also disclosed a process for the preparation of cabazitaxel.
4α-Acetoxy-2α-benzoyloxy-5β,20-epoxy-1β,13α-dihydroxy-7β,10β-dimethoxy-9-oxo-11-taxen (7β,10β-dimethoxy-10-deacetoxybaccatin III) is a key intermediate for the preparation of cabazitaxel.
We have found an improved process for the preparation of 7β,10β-dimethoxy-10-deacetoxybaccatin III. The process of the invention results in higher yields compared with the known process of using different solvent in the reaction.
We have also found a novel process for the preparation of cabazitaxel. The process of the present invention is simple, inexpensive, reproducible and is well suited on an industrial scale.
Thus, one object of the present invention is to provide an improved process for the preparation of 7β,10β-dimethoxy-10-deacetoxybaccatin III.
Another object of the present invention is to provide a novel process for the preparation of cabazitaxel.